Commercial decaffeination techniques often involve solvent extraction from pre-wetted whole green beans such as described by Patel et al. in U.S. Pat. No. 3,671,263 who use a chlorinated hydrocarbon solvent, and by Berry et al. in U.S. Pat. No. 2,309,092 who use a caffeine-deficient aqueous solution of coffee solubles.
Recently, a decaffeination method was disclosed in U.S. Pat. No. 3,879,569 to Vitzthum et al. wherein quantitative extraction of caffeine from raw coffee beans is achieved with moist, liquid carbon dioxide at a pressure above the critical pressure. Also, in U.S. Pat. No. 3,806,619 to Zosel, caffeine is extracted from green coffee by moist supercritical carbon dioxide, and in U.S. Pat. No. 3,843,824 to Roselius et al. caffeine is extracted from roasted coffee by contact with moist supercritical carbon dioxide. These procedures, like the earlier solvent processes, however, require that the beans be wetted to obtain efficient rates of extraction.
It has been the experience of the prior art that even the strongest caffeine solvents previously employed could not effectively decaffeinate dry, green coffee beans.